Automatic knockoff device for oil well pumping apparatus



April 14, 194-2. 2,279,950 AUTOMATIC KNOCK-OFF DEVICE FOR OIL WELL PUMPING APPARATUS C.YA. MG AY Filed July 28, 1939 n ZSheeis-Sheet 1 moa /4 M- /(ag 'C/ar INVENTOR ATTORNEY c. A. McKAY 2,279,950 AUTOMATIC KNOCK-OFF DEVICE FOR OIL WELL PUMPING APPARATUS I 'April 14, 1942.

Filed July 28, 1959 I 2 Sheets-SheetZ Gare/7C8 7 INVENTOR ATTORNEY Patented Apr. 14, 1942 AUTQMATIC KNOCKOFF DEVICE-FOR OIL WELL PUMPD'IG APPARATUS Clarence A. McKay, Tulsa, Okla.

Application July 28, 1939, Serial No. 287,142

16 Claims. .(.Cl. 1(l3-23) The invention relates to automatic knock-offs for oil well pumping apparatus, and has for its object to provide means whereby the shackle rod leading to a pump jack is automatically disconnected from the power line when the well is pumped to a predetermined level.

A. further object is to control the automatic knock-off mechanism on the down strokes of the pump plunger as it has been found that on the down stroke of the plunger various degrees of slack develops in the shackle rod when the oil level in the well approaches various levels.

A further object is to provide an automatic latching means in connection with a shackle rod whereby the shackle rod is held against reciprocation when the fluid level in the well reaches a predetermined position, at which time the shackle rod straightens incident to reduced fluid resistance in the well, thereby preventing further operation of the sucker rod and pump plunger and damage to said pump plunger incident thereto, that is, operation when the fluid level in the well is below the pumping level.

A further object is to provide an automatic knock off for a shackle rod leading to a pumping jack and connected to a power line, and to provide means cooperating with the knock off mechanism and carried by the shackle rod, which means is in an inoperative position on the upstroke of the pump plunger and on the down stroke of thepump plunger under normal pumping operations, at which time the shackle rod is substantially straight during the upward strokes and sagged' on the downward strokes, and in operative position for the knock-off when the shackle rod is on the downward stroke when the fluid level in the well is low and the shackle rod is straightened out, incident to reduced fluid pressure in the well against the pump plunger.

A further object is to provide the shackle rod with a predetermined lock bar to which the power rod is detachably connected, and latching means cooperating with the lock bar and controlled by reduction of fluid resistance within the well on the down strokes of the pump plunger, which will cause the shackle rod to straighten and cooperate with the latching means.

A further object is to provide the drop bar with e trip rod holding member, spring actuated, and the trip bar with a trip lever in the path of a trip disc carried by the shackle rod and normally out of the path of the trip lever and carried by the sag portion of the shackle rod and in the path of the trip lever when the shackle rod is straightened on the down stroke incident to lack of fluid resistance within the well when the fluid level reaches a predetermined position.

A further object is to provide variable weight means in connection with the shackle rod for 1 adjusting the sag thereof in relation to the trip lever and means for adjusting the trip lever vertically and longitudinally in relation to the trip disc for proper timing of the latching operation;

With the above and other objects in view the invention resides in the combination and arrangernent of parts as hereinafter set forth, shown in the drawings, described and claimed, it being understood that changes in the precise embodiment of the invention may be made within the scope of what is claimed without departing from the spirit of the invention.

In the drawings:

Figure l is a longitudinal sectional view through the knock-01f device, showingthe same set for automatic operation and the sag of the shackle rod for clearing the tripping mechanism under normal pumping conditions. a

Figure 2 is a view similar to Figure 1, showin the device tripped for a knock-off operation, and the extreme movements of the parts in dotted lines. 7

Figure 3 is a perspective viewof the knock-off mechanism.

Figure 4 is a perspective view of the tripping mechanism.

' Figure 5 is a View in elevation of the tripping The knock-off device hereinafter. set. forth is I disposed between the source of power which reciprocates the power rod 1 andthe shackle rod 2 which leads to aconventional form oflpumping jack, which pumping jack moves thev sucker rod in the well and the pump plunger in the usual manner. The knock-offs for the various pumping lines are usually located adjacent the power house; and the power rod or line and the shackle rod are reciprocated usually by a horizontal eccentric; all of which is old and conventional structure. It is'desirable to disconnect various shackle rod whenthe liquid level in a particular well reaches a predetermined low to prevent wear and damage to the pump plunger andcups thereon incident to continued operation after a particular well has been pumped off. Heretopump plunger and in the direction of the arrow b on the down stroke of the plunger. Under normal pumping conditions there is a sag in the shackle rod on the down strokes of the plunger incident to the fluid resistance in the well, however as the fluid level lowers in the well the weight of the plunger and the sucker rod 1 straightened out the shakle rod ,on the down stroke incident to reduced fluid resistance in the well and this operation raises the trip disc 3 into the path of the hinged trip lever 4. It will be noted that when there is fluid resistance in the well, the shackle rod sags to the dotted line position .shown'in Figure 1 so the disc 3 will clear the trip lever 4 and that on the movement of the shackle rod in the direction of the arrow a, at which time the shackle rod is straightened out, the disc 3 will, cam under the hinged trip lever without actuating the trip rod 5. This operation continues until the liquid level within the well reaches a predetermined position and reduces the liquid resistance against the pump plunger, thereby allowing the weight of the pump plunger and sucker rod to straighten out the shackle rod on the down strokes of the plunger, and at which time the tripping mechanism comes into' operation. a I

One end of the shackle rod has connected thereto a sliding lock bar 6, which reciprocated therewith, and the lock bar extends through a knock-off post I and is slidably mounted in guide shoes .8. One end of the slidable lock bar is provided'with an eye 9, in which is connected the hook l0 carried by the power line I. It will be seen that as the power line I is reciprocated the shackle rod will reciprocate therewith. It

will be noted that the hook I0 hooks upwardly" through the eye 9 and when the lock bar 6 gravity operated. The lock bar I2 is held in raised inoperative position shown in Figure 1 by means of the trip rod 5, the end [3 of which extendsthrough an'aperture l4 in the drop bar and an aperture IS in the member H. The end l3 of the trip rod 5 is normally held in the position shown in Figure 1 by means of an expansion spring l6, surrounding the trip rod and interposed between the bearing ll of one of the spaced supports! and the adjusting collar I9.

Trip rod 5 is provided with a travel limit collar 7 20, which engages one end of the rod supporting bracket 2|.

Adjustably, mounted on the trip rod 5 is a bracket-22 which supports the trip lever 4, pref-v erably by means of adjustable bolts 23 so that the trip lever may be adjusted downwardly or upwardly in relation to the operating disc 3, carried by the shackle rod. It will be noted that the trip lever 4 is provided with an upwardly extending arm 24, whichlimits the pivotal action of the trip lever beyond a vertical position in one direction, however it will be noted that the trip lever is free to.swing in the opposite direction for camming over the disc 3 during the reciprocation of the disc. In some cases, to obtain a proper positioning of the disc 3 in relation to the trip lever and in relation to the sag of the shackle rod, it is desirable to provide weight means on the shackle rod 2 as shown in Figure 2. This weight means comprises downwardly extending eye bolts 25 on opposite sides of the trip disc 3 and a plurality of weights 26 on said bolts. These weights may be varied in number according to the amount of sag in the shackle rod. The weights also centralize the sag adjacent the trip lever 4 for insuring a positive operation. Under some conditions it has been found that weights can be advantageously used.

In operation, under normal pumping conditions, the sucker rod 2 is reciprocated as shown in full and dotted lines in Figure 1, so that on the up strokes of the plunger, when the shackle rod carries the weight of' the. plunger and sucker rod, the shackle rod is straightened out and the disc will cam by the trip lever 4. 0n the down stroke of the plunger and sucker rod the shackle rod will sag as shown in dotted lines in Figure l incident to the fluid resistance inthe well and the trip disc 3 will pass under the trip lever 4.

When the well is pumped off or the liquid level in the well is dangerously low for the pumping operation the fluid resistance against the pump plunger is reduced and the weight of the pump plunger and sucker rod will, straighten out the shackle rod so the trip disc 3 is raised into the path of the trip lever 4 on the down stroke. When this takes place the trip rod 5 is axially moved in the direction of the arrow 0 so that the end l3 thereof is pulled out of the aperture I4 of the drop bar I2, and the drop bar will drop by gravity downwardly against the upper side of the lock bar 6, and when the lock bar again moves in the direction of the arrow :1, the drop barwill'engagein the notch 21 in the upper side of the lock bar and will hold the same against reciprocation to the left so that the hook ID will disengage from the eye 9 upon' reverse movement of the power line I.

From the above it will be seen that an automatic knock-off is provided for a shackle rod, which is controlled by the sag in the shackle rod, and which sag is controlled by the reduction of fluid resistance to a pump plunger within the well.

- The invention having been set forth what is claimed as new and useful is:

1. A well knock-off device comprising a reciprocating lock bar, a power line detachably connected to one end of the lock bar, a flexible shackle'rod connected to the other end of the lock barand leading to a pumping apparatus, said shackle rod normally sagging during a pumping operation and straightening out on the down strokes of the pumping operation when the'liquid level in the well approaches a predetermined point, latching mechanism for the lock bar and means carried by the shackle rod and positioned to engage and trip the latching mechanism when the shackle bar straightens out on the down strokes of the pumping apparatus when the liquid level within the well approaches said predetermined point.

2. 'A device as set forth in claim 1 wherein the latching device comprises a drop bar above the lock bar, a trip rod for normally maintaining the drop bar in inoperative position, a hinged trip lever carried by thetrip rod above the shackle rod and a member carried by the shackle rod and positioned to pass under the trip lever on normal pumping operation incident to the sag in the shackle rod and camming past the trip lever in one direction.

3. A device as set forth in claim l wherein the latching mechanism comprises a latching bar adapted to engage and hold the lock bar against reciprocation in one direction, a rod for holding the lock bar in inoperative position under normal pumping conditions, an operating lever for said bar and a member carried by the shackle rod in the sag thereof for passing under the trip lever and movable into the path of the trip lever incident tothe reduction of sag in the shackle rod when the fluid level in the well reaches a predetermined point for causing the latching bar to hold the lock bar against reciprocation.

4. The combination with an oil well knock-off device comprising a reciprocating lock bar connecting the power line and a shackle rod, said shackle rod having various degrees of sag incident to fluid resistance within a well and substantially straightening out on the up strokes of the plunger under normal pumping conditions, sagging on the down strokes of the plunger under normal pumping conditions and straighteningout on the down strokes of the plunger when the liquid level in the well approaches a predetermined point, of lock bar holding mechanism, said lock bar holding mechanism being normally inoperative and operative through the medium of the shackle rod when the pump plunger is on its down stroke and the liquid level has been lowered to a predetermined position.

5. A device as set forth in claim 4 wherein the latching mechanism for the lock bar is controlled by a member mounted on the shackle rod and a hinged trip member with which the shackle rod member engages when the she ckl e rod straightens.

6. A device as set forth in claim 4 wherein the latching device is provided with a hinged trip lever hingedly movable in one direction, a trip disc carried by said shackle rod in the path of the trip lever and adapted to pass below the trip lever incident to sag in the shackle rod under normal pumping conditions and to cam over the trip lever in one direction under normal pumping conditions and to engage the trip lever and actuate the latching mechanism upon straightening out of the shackle rod on the down stroke of the plunger when the liquid level in the well reaches a predetermined point and weight means for adjusting the period of operation of the latching device.

7. The combination with an oil well apparatusreciprocating a sucker rod through the me dium of a reciprocating shackle rod, said shackle rod being bowed downwardly during pumping in the shackle rod when the liquid level in the well reaches a predetermined point.

9. The combination with a well pump apparatus including a sucker rod, said apparatus being controlled by a reciprocating shackle rod normally having a bow therein, a knock-off mechanism adjacent to and actuated by said shackle rod and normally inoperative and means carried by the shackle rod and controlled by lack of bow in the shackle rodfor operating the knock-off mechanism when the liquid level in the well reaches a predetermined low.

10. A well pumping apparatus including a reciprocating normally sagging shackle rod, knockoff mechanism in connection with said shackle rod said mechanism being normally in inoperative position during normal pumping operations and means cooperating with the shackle rod at a point spaced from its .ends and so arranged and constructed when the liquid level in the well reaches a predetermined low and the sag in the shackle rod is reduced said knock-01f mechanism will be operated.

CLARENCE A. McKAY. 

